Safety valve structure for hydraulic jacks

Abstract

A hydraulic jack safety valve structure provided within the one-way valve body of the jack. The one-way valve has a cylindrical shape and is provided on the pump base of the jack. An annular slot is provided in the cylindrical body. The annular slot is provided with an oil inlet port and an L-shaped oil inlet passage which extends from the top surface of the one-way valve. An oil discharge port is provided so that the top of the one-way valve communicates with the bottom. The wall of the annular slot is provided with a safety oil discharge port which communicates with the oil discharge passage. Inside the safety oil discharge passage, a push pin and a safety spring are inserted in proper sequence. An adjustment screw is used to secure the pin and spring in place. The push pin, inside the safety oil discharge passage, provides flow guidance so that the flow of the hydraulic discharge fluid can be smooth.

What is claimed is: 
     
       1. A valve for a hydraulic jack comprising: a cylindrical valve body having an annular exterior wall having therein an annular recess;   a fluid inlet port formed in said recess;   a first port formed in an upper surface of said valve body;   a first passage, which is L-shaped, extending through said valve body from said first port to said fluid inlet port, wherein a longer leg of said L-shaped first passage includes a larger width portion extending from said upper surface of said valve body and a smaller width portion extending downwardly from said larger width portion;   a ball and spring provided in said larger portion of said fluid inlet passage, said spring engaging a radial wall portion projecting inwardly from an inner peripheral surface of said first passage, wherein said ball is positioned between an upper end of said smaller width portion and said spring;   a second port formed in said upper surface of said valve body;   a port formed in a bottom surface of said valve body;   a second passage extending through said valve body from said second port to said bottom surface port, wherein said second passage includes a larger width portion extending upwardly from said bottom surface port and a smaller width portion extending from said larger width portion to said second port;   a ball and spring provided in said larger width portion of said second passage, said spring engaging a radial wall portion projecting inwardly from an inner peripheral surface of said second passage, wherein said ball is positioned between a lower end of said smaller width portion of said second passage and said spring;   a safety fluid discharge port in said recess;   a port formed in a sidewall of said second passage at said smaller width portion;   a third passage extending through said valve body from said safety fluid discharge port to said port formed in said inner sidewall of said second passage, wherein said third passage includes a smaller width portion extending from said sidewall port and a larger width portion extending from said safety fluid discharge port;   a member, provided in said larger diameter portion, having an axial hole therethrough;   a push pin in said larger width portion of said third passage, said push pin having a cone shaped portion including an apex which extends into said smaller width portion and a rod extending from said cone shaped portion through said member to guide linear movement of said push pin;   a spring interposed between said push pin cone shaped portion and said member, said spring biasing said cone portion into engagement with an end of said smaller width portion of said third passage.   
     
     
       2. The valve as claimed in claim 1, wherein said larger width portion of said third passage is at least partially threaded and said member provided in said larger width portion of said third passage comprises an adjustment screw having a threaded exterior surface. 
     
     
       3. The valve as claimed in claim 1, further comprising a filtering screen provided in said fluid inlet port. 
     
     
       4. The valve as claimed in claim 1, wherein said rod comprises a large diameter portion extending from said cone shaped portion and a small diameter portion which extends from said large diameter portion through said member.